NOMA-GAP/ARHGAP33 regulates synapse development and autistic-like behavior in the mouse

Neuropsychiatric developmental disorders, such as autism spectrum disorders (ASDs) and schizophrenia, are typically characterized by alterations in social behavior and have been linked to aberrant dendritic spine and synapse development. Here we show, using genetically engineered mice, that the Cdc42 GTPase-activating multiadaptor protein, NOMA-GAP, regulates autism-like social behavior in the mouse, as well as dendritic spine and synapse development. Surprisingly, we were unable to restore spine morphology or autism-associated social behavior in NOMA-GAP-deficient animals by Cre-mediated deletion of Cdc42 alone. Spine morphology can be restored in vivo by re-expression of wild-type NOMA-GAP or a mutant of NOMA-GAP that lacks the RhoGAP domain, suggesting that other signaling functions are involved. Indeed, we show that NOMA-GAP directly interacts with several MAGUK (membrane-associated guanylate kinase) proteins, and that this modulates NOMA-GAP activity toward Cdc42. Moreover, we demonstrate that NOMA-GAP is a major regulator of PSD-95 in the neocortex. Loss of NOMA-GAP leads to strong upregulation of serine 295 phosphorylation of PSD-95 and moreover to its subcellular mislocalization. This is associated with marked loss of surface α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) receptor and defective synaptic transmission, thereby providing a molecular basis for autism-like social behavior in the absence of NOMA-GAP.